It is generally known that a catadioptric lens system having a reflective system and a refractive system is highly advantageous in reducing the length of the whole lens and reducing chromatic aberration, and is configured to be appropriate for a long-focus lens. For example, in JP-A-55-32023, it is possible to obtain favorable imaging performance through a catadioptric lens system that includes, in order of light travel, a positive single lens, a primary rear surface reflection mirror having a negative meniscus shape, a secondary rear surface reflection mirror having a positive meniscus shape, and a lens group having a negative refractive power.
As focusing modes of the catadioptric lens system, a mode of varying the length of the whole lens, such as a mode of extending the whole lens or a mode of changing a space between two reflective surfaces, have been generally used. Further, for example, JP-A-58-205124 discloses a catadioptric lens system of an inner focusing mode in which the length of the whole optical system is invariant. The catadioptric lens system includes, in order of light travel: a first lens group that includes a reflecting member and has a positive refractive power; and a second lens group that is movable along the optical axis and has a negative refractive power; and a third lens group that has a positive refractive power. In the system, in a state where the focus is at infinity, an afocal system is formed of the first lens group and the second lens group, and the second lens group is moved to be close to the image side, whereby a close-range object is brought into focus.
Meanwhile, in recent years, there have been provided so-called single-lens mirrorless cameras each having portability which is improved by removing mirrors from a single-lens reflex camera so as to simplify a camera structure. The single-lens mirrorless camera is appropriate to capture a moving image with high image quality since light constantly reaches an imaging device for image capturing contrary to the single-lens reflex camera. Further, a so-called wobbling technique has been used. In the technique, in the case of capturing a moving image, when an object is shifted back and forth relative to a camera during capturing, in order to bring the object into focus, the focal point is shifted in a direction capable of obtaining a high contrast value by minutely wobbling the focal point. When the focusing group is intended to perform the wobbling action, it is preferable that the focusing group be configured to have a small size and be lightweight as much as possible by setting a focusing mode to the inner focusing mode. By making the focusing group have a small size and be light, it is possible to reduce the size of the whole lens including a driving mechanism of the focusing group, and it is possible to reduce power consumption caused by focus driving.